Objectives To compare the responsiveness of disease-specific (Arthritis Impact Measurement Scale 2, AIMS2),1,2 generic (Medical Outcome Study Short Form Health Survey, SF-36)3 and preference-based instruments (rating scale, RS and time trade off, TTO)4 to changes in particular status and perceived health in patients with rheumatoid arthritis (RA).
Methods Seventy-eight consecutive patients with RA, attending the care facilities of the Department of Rheumatology of Ancona, were recruited to the longitudinal study. Changes in global disease activity assessed by using the EULAR criteria were used as external indicators of improvement/response. In order to assess the responsiveness three strategies were used: 1) effect size (ES, mean change/standard deviation of baseline values); 2) standardised response mean (SRM, mean change/standard deviation of change in stable subjects); and 3) receiver operating characteristic method.
Results There were 55 women and 23 men with a mean age of 56 years (range 19–78 years) and arthritis duration of 7.1 years (range 6 months-24 years). By using a 3 category EULAR criteria for improvement/response, 21 (27%) patients reported a good improvement, 23 (29,5%) moderate improvement, and 34 (43,5%) no changes in their arthritis over 12 months. The mean change score in generic and specific health status instruments and in utility measures, were significantly related to response category. There were no significant differences in responsiveness between SF-36 and AIMS2 in patients with RA when using changes in global disease activity as external indicator. The pain subscales were most sensitive to measure change over time, followed by physical function and psychosocial subscales. For the utility measurement, RS scores were found to be more responsive in detecting significant changes in preferences than TTO scores.
Conclusion The results suggest that both the SF-36 and AIMS2 may prove suitable for the assessment of health perception outcomes in RA clinical trials. Concerning the patient utilities the RS method appeared to be more responsive than TTO method. New strategies for assessing sensitivity to small changes should be developed and applied to health status and utility measures.
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